'94 D90 tune-up fail - Defender Source
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  #1  
Old June 11th, 2014, 01:07 AM
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Micah Cobb
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'94 D90 tune-up fail

My 90 would start and idle just fine, but would sputter and loose power under load /acceleration. I replaced the fuel filter but problem persisted. I then assumed it was an ignition problem.

I replaced coil, cap, rotor with NO change. Plugs and wires look OK.

Pulled distributor and replaced the ignition module.

Reinstalled distributor and now truck won't start at all. Went through the TDC routine, confirmed plug wire position, etc. Reinstalled dizzy with rotor 30 deg CCW from #1...once fully in place the rotor looks to be on #1.

After going thru this routine a couple of times, I eventually reinstalled the old IM as the truck still ran prior to replacing the IM and messing with the dizzy. This had no effect.

I am pulling my hair out! What in the heck did I do wrong? I obviously need to get it running in order to further diagnose the original sputtering/ no power issue.
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  #2  
Old June 11th, 2014, 01:27 AM
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Micah Cobb
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I will add that there is good spark. Fuel pump primes then shuts off.

MAF wire connection is good.
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  #3  
Old June 11th, 2014, 08:00 AM
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Check the wire connections to the coil. Perhaps the ecu wire connection is poor resulting in the injectors not firing.
You could also pull a plug and sniff for fuel.
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  #4  
Old June 11th, 2014, 08:13 AM
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Chris Davis
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You might be firing,on the exhaust cycle in lieu of compression-- try reinstalling dizzy 180 degrees
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  #5  
Old June 11th, 2014, 08:42 AM
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...you're sure the intake tubes / hoses are all connected...air filter housing to air meter / air meter to throttle body...right?
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  #6  
Old June 11th, 2014, 10:08 AM
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Micah Cobb
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Quote:
Originally Posted by Davis View Post
You might be firing,on the exhaust cycle in lieu of compression-- try reinstalling dizzy 180 degrees
So, reinstall dizzy body 180 degrees off of where it should be?

Or are you saying to have rotor pointing 180 off of #1?

------ Follow up post added June 11th, 2014 08:10 AM ------

Quote:
Originally Posted by UnfrozenCaveman View Post
...you're sure the intake tubes / hoses are all connected...air filter housing to air meter / air meter to throttle body...right?
Yes, I checked and truck ran after that.
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  #7  
Old June 11th, 2014, 10:10 AM
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that is my guess as well 180 out on the timing

The piston goes up and down 2x the piston will be in what looks like TDC at the top of one compression stroke and one exhaust stroke it is common to think you are on TDC but off by 180 so what Chris is saying is that maybe you installed the dist on the exhaust stroke instead of the compression stroke IE 180 out.

Hope that helps

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  #8  
Old June 11th, 2014, 10:12 AM
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Micah Cobb
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To be clear...the truck ran after intake hose check.

Truck still does NOT run after IM and dizzy removal/ replacement.
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  #9  
Old June 11th, 2014, 11:11 AM
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Micah Cobb
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How do I fix the 180 degree out-of-time issue?

------ Follow up post added June 11th, 2014 09:12 AM ------

Dave...just saw you post. I'll check it out.

Thanks all for the help thus far.
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  #10  
Old June 24th, 2014, 11:59 PM
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Let us know how it goes!!
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  #11  
Old June 25th, 2014, 04:25 PM
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Micah Cobb
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Yep, it was 180 deg out. I rectified that and it fired right up.

Idles great and revs while parked.

However, when driven, it still sputters and backfires like it did before I began the tune-up.

I want to test the Vehicle Speed Sensor...

I bought the Workshop Manual but it did not come with the Electrical testing manual, so I'm not sure how to test the VSS.

Any ideas on this? Any thoughts on what else could cause the problem?
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  #12  
Old June 25th, 2014, 05:21 PM
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Micah Cobb
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Yes.

Replaced Fuel Filter, coil, and rotor. Inspected dizzy cap and plug wires.

The sputtering and backfiring occurred a couple of days after my wife drove home in a downpour. Maybe water in an ECU connector?
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  #13  
Old June 25th, 2014, 05:23 PM
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Quote:
Originally Posted by mc298 View Post
Yep, it was 180 deg out. I rectified that and it fired right up.

Idles great and revs while parked.

However, when driven, it still sputters and backfires like it did before I began the tune-up.

I want to test the Vehicle Speed Sensor...

I bought the Workshop Manual but it did not come with the Electrical testing manual, so I'm not sure how to test the VSS.

Any ideas on this? Any thoughts on what else could cause the problem?
whats the timing ?? did you set it up with the vacuum connected or disconnected?
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  #14  
Old June 25th, 2014, 05:40 PM
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Micah Cobb
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The problem occurred before I ever touched the ignition system. I started the tune up assuming that the cause of the sputtering and back firing was ignition-related....water in dizzy, etc. However none of those components appears to be the culprit.

I inadvertently reinstalled the OLD ignition module during the course of all of this. However, given that the truck idles and revs great while parked makes me think that the module is fine.

Timing is close to where it was. Need to fab extensions for my timing light and set timing exactly before extended driving.

The vacuum advance line is in good shape with no leaks.

Now I am thinking VSS or other issue since the problem happened coincidentally after being driven in a downpour.
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  #15  
Old June 25th, 2014, 05:48 PM
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Funny my issue started with a tune-up as well.

Also you should be able to hook the timing light up locally under the hood using main ground and alternator output to give you some additional slack.
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  #16  
Old June 25th, 2014, 06:11 PM
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Micah Cobb
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The dashpot being the brass colored diaphragm?
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  #17  
Old June 25th, 2014, 06:14 PM
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Yes, suck on the rubber hose to test
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  #18  
Old June 25th, 2014, 07:59 PM
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Don't assume your module is alright just because you idle good. I don't know if it was a good spare or suspect, but if it was suspect I would swap in a known good just to rule that out. Are you running a stock distributor? There is a little plastic piece in them that sometimes gets brittle and breaks and can cause some issues. If you take off the rotor, then unscrew the plastic protecting plate, you will see what I think is a circlip on the shaft and under that a washer and a plastic ring--I am pretty sure that is what broke on mine and caused me some head ache to be sure. It was on my RRC, but same deal.
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  #19  
Old July 19th, 2014, 09:59 PM
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Micah Cobb
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OK Team...

After much delay and after double-checking timing....I fixed the o-ring located in the joint between the MAF and the air filter housing, which had a split in it, possibly allowing the MAF to ground on the housing. The 90 still stumbled under load....

So, I went back to the circumstances around when the problem began ....the truck began stumbling/ hesitating after being driven home in a downpour and parked for a few days.

When chatting with an old Houston Land Rover Club pal, he recalled a story of another member's 90 taking on water through the wiring harness, which found its way into the ECU. I pulled my ECU and water started pouring from it as I was handling it. After I took the ECU apart, I dried the circuit board with a hair drier.

Reassembled the ECU, and the truck fired right up. Acceleration is restored, and she runs great!

Now, I need to figure out how to seal the harness and ECU.

Thank you to all of you who helped out along the way!
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  #20  
Old July 20th, 2014, 02:29 PM
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Dielectric grease and a zip lock baggie works wonders, long term visit the container store and find box you can seal.
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